1. Field of the Invention
This application relates to a system and method that improves the Steam-Assisted Gravity Drainage (SAGD) facility or other Enhanced Oil Recovery (EOR) facilities with a system that can be integrated into an existing facility or be used as a new stand-alone facility. The present invention relates to processes for producing steam from low quality rejected water containing high levels of dissolved and suspended inorganic solids or organics, such as oil.
With its simple direct contact, above ground adiabatic nature, and its high pressure and temperature solid removal, this invention will minimize the amount of energy used to produce the mixture of steam and gas injected into the underground formation to recover heavy oil. This thermal efficiency minimizes the amount of greenhouse gases released into the atmosphere.
This thermal efficiency is achieved due to direct heat exchange. The condensed steam and the gases that will return back to the surface with the produced bitumen are at the underground reservoir temperature, which is no higher than the temperature required for oil recovery. The produced water does not need to be cooled to be treated in a water treatment facility as the produced hot contaminated water can be used for steam production without any additional treatment. (See “Alternative Energy Source” by Rosalynn J. MacGregor in Hydrocarbon Processing, July 2007, discussing the significance of the SAGD produced water cooling requirement on a SAGD facility heat balance and the heat losses that result in greenhouse gas (GHG) emissions.)
The above-mentioned invention also relates to processes for making SAGD facilities or other EOR facilities more environmentally friendly by using low quality fuel and reducing the amount of greenhouse gas emissions through thermal efficiency and injecting the CO2 into the underground formation, where a portion will remain permanently.
2. Description of Related Art Including Information Disclosed Under 37 CFR 1.97 and 37 CFR 1.98
Steam injection into deep underground formations has proven to be an effective method for EOR facilities producing heavy oil. This is typically done by SAGD or by Cyclic Steam Stimulation (CSS), also known as “huff and puff”. In recent years, the SAGD method has become more popular, especially for heavy oil sand formations. Presently, steam injection is the only method commercially used on a large scale for recovering oil from oil sands formations.
The invention can be used together with prior art processes being used in upstream and downstream production facilities, currently in use by the oil Industry. The present invention adds the adiabatic direct contact steam and carbon dioxide generation unit to reduce the disadvantages of the prior art and to allow for expansion with use of a low quality water supply, reject water from existing facilities and the use of low quality fuel supplies. Also, there is no need for high quality separation of the oil from the produced water and water purification processes with this invention. The present invention is a Zero Liquid Discharged (ZLD) system because solid waste is produced instead of liquid waste.
In the present invention, the exothermic reactions and treatment of the injected gas mixture are done in an adiabatic control area above ground. The underground portion of oil production is very complex, with many unknowns, because the oil formed over millions of years until it reached steady-state equilibrium. As shown in other areas, one way to exploit resources and produce products is by improving processes control. Since underground combustion processes change the chemistry of the reservoir, they further complicate the complex underground reservoirs and are difficult processes to control.
The injection of pure steam, or steam in a mixture with other gases, creates the minimum necessary increase in the underground formation disorder. It does not increase the complexity of the underground reservoir beyond the minimum required to mobilize oil from the sand. This may be the reason why only the processes of steam-injection (or of steam and other gases), are implemented and found to be commercially effective with SAGD.
The present invention is to be used with EOR methods, mainly SAGD. The main disadvantages of existing commercial SAGD(s) are the main drivers of the present invention.
SAGD, CSS and similar EOR facilities, consume large quantities of water to extract the heavy oil by using steam. The water-to-oil ratio needed to extract the oil from the ground is about 2-4 barrels of water to one barrel of oil. The current prior art technologies require relatively high water quality, as required by the Once-Through Steam Generators (OTSGs) or boilers for scaling prevention. This results in expensive water treatment plants with water de-oiling separation. The operations of such facilities consume chemicals to minimize oil traces in the recycled water. Reject water is produced and injected into disposal wells. In the case of lime softeners, sludge is produced as well. The purification processes can create sludge (as is the case with lime softeners) and reject wastewater. Where disposal wells are not permitted for environmental reasons, an additional expensive and energy consuming ZLD system is added to evaporate the reject water to produce solid waste. As part of the recycled water treatment, all oil traces must be removed. These stringent requirements are applicable in both prior-art commercial technologies, lime softeners and in evaporator-based facilities. Any oily emulsions must be broken down by chemicals or filters to a very high degree of separation. The process usually produces a stream of “reject water” from the blow-down that is injected into disposal wells or treated in an additional, expensive and energy consuming ZLD facility, including evaporators and crystallizers. Low quality, high Total Suspended Solids (TSS) and Total Dissolved Solids (TDS) source water requires an expansive treatment facility, and using lime softeners creates large amounts of sludge. As a result the oil sands producing companies are typically drawing relatively high aquifers to produce the best water quality available from an area, which is typically a much larger area than the area in which the oil is produced.
An ongoing portion of the EOR construction and operation costs is the cost of constructing and operating the water treatment plant. At present, the most widespread commercial water treatment process in the SAGD industry is the use of lime softeners. In this process, lime, magnesium oxide and other materials are used to remove dissolved solids from the water in the form of slurry. This process requires constant chemical supply and creates significant amounts of slurry waste, resulting in landfill costs and environmental impacts. Different processes include evaporators that require water de-oiling and reject water that must be disposed of in disposal wells, or evaporated and crystallized to produce solid waste in additional ZLD facilities. (See “Use of Evaporation for Heavy Oil Produced Water Treatment”, by W. Heins and D. Peterson, Journal of Canadian Petroleum Technology, 2005, vol. 44, pp. 26-30.) There is a need for the ability to use oily water and water-oil emulsions in the production of steam so as to reduce the complexity of water treatment and associated capital costs. As well, it is necessary to do so in order to reduce the amount of energy and chemicals used. There is an advantage to producing dry solid waste that is easy to dispose of.
EOR facilities, like SAGD, consume a large amount of heat energy. In most commercial SAGDs, natural gas is used as the energy source for steam production. Natural gas is a valuable resource. The extensive use of natural gas for producing oil is expensive with significant environmental impacts. In some prior art projects, steam is produced by burning some of the extracted heavy oil for the production of steam. This is a problematic process since there is a need for flue gas treatment prior to releasing it into the atmosphere. Another option is to combine upstream and downstream technologies in the form of an SAGD and an Upgrader that uses a gasification process to gasify the “barrel bottom” to produce syngas for the production of steam in non-direct steam generators. There is a need to use heavy oil upgrading by-products for steam production.
The SAGD technology consumes a significant amount of energy to produce the steam for SAGD facilities. The use of OTSG, boilers or gas turbines to generate steam causes only a portion of the heat from the burning hydrocarbon to be injected underground into the reservoir. Hot flue gases with carbon dioxide are released to the atmosphere. A typical SAGD that produces 50,000 bitumen barrels per day generates 4,000 ton to 8,000 ton of carbon dioxide per day. There is a need to minimize the carbon dioxide release. This can be achieved by: (1) using less steam; (2) producing the steam in a more efficient manner, (so as to minimize aboveground heat losses); and (3) injecting the carbon dioxide with the produced steam to the reservoir; where some of it will permanently remain.
Various patents have been issued that are relevant to this invention. For example, U.S. Pat. No. 4,498,542, issued on Feb. 12, 1985 to Eisenhawer et al., describes a system for above-ground direct contact steam generation. The method and apparatus produce a high-pressure mixture of steam and combustion gases for thermal stimulation of petroleum wells. The produced mixture of combustion products, such as steam and water, is separated to gas and liquid phase in a separator where the gas and steam mixture is injected to create enhanced oil recovery. The liquid water is flashed to produce additional steam. The concentration of solids increases downstream from the combustion in the separator and flash chamber where they are continually removed with disposed, drained water. The drained water's heat energy is reused in this process. The generated steam in the saturated condition will create corrosion problems and will require additional steps to be taken.
U.S. Pat. No. 4,398,604, issued on Aug. 16, 1983 to Krajicek et al., describes a system for above-ground stationary in direct contact horizontal steam generation. The method and apparatus produce high pressure, a thermal water vapor stream, and a stream of combustion gases for recovering heavy viscous petroleum from a subterranean formation. These high-pressure combustion gases are directed into a partially water-filled vapor generator vessel used to produce a high-pressure stream of water vapor and combustion gases. The generated solids are continually removed with reject water.
There are also patents related to applications in down-hole heavy oil production. U.S. Pat. No. 4,463,803, issued to Wyatt on Aug. 7, 1984 describes a system for down-hole stationary direct contact steam generation for enhanced heavy oil production. The method and apparatus generate high-pressure steam within a well bore. The steam vapor generator is used for receiving and mixing high-pressure water, fuel and oxidant in a down-hole configuration. The produced solids are discharged to the reservoir. Generally, the down-hole direct contact steam generators of the prior art have some debilitating disadvantages. Any maintenance is complicated, and requires the well to shut down, while a drilling completion rig is necessary to pull out the equipment. The water and fuel that is used must be of the highest quality so as to prevent the creation of solids that plug up the well over time. Any operation outside of optimal design conditions can lead to corrosion and solid carbon problems.
The above-ground prior art methods and systems typically generate reject water that can be either released to a disposal formation or crystallized in a separate facility, where the remaining water is evaporated. The steam and carbon mixture produced by the prior art can easily lead to corrosion, due to condensation. The prior art also requires a liquid-solid separation process.
It is a goal of the present invention to provide a system and method to improve EOR facilities like SAGD, through a supply of steam and gas mixtures for underground injection wells and also by creating add-ons to existing facilities.
It is another objective of the present invention to provide a system and method that can produce steam from low quality rejected water containing high levels of TDS and TSS, like high levels of non-dissolved inorganic solids or organics.
Another objective of the invention is to provide a system and method that utilizes low-grade fuel.
An additional objective of the present invention is to provide a system and method that will remove produced solids by converting the liquids to gas phase under high pressures and will remove solids from the gas phase.
Furthermore, it is another objective of the present invention to provide a system and method that enhances thermal efficiency as a result of direct heat exchange, which minimizes the amount of energy used to produce the mixture of steam and gas injected into the underground formation to recover heavy oil.
It is a further objective of the present invention to provide a system and method that minimizes the amount of greenhouse gases that are released out into the atmosphere.
A further purpose of the present invention to provide a system and method that serve to make EOR facilities, like SAGD, more environmentally friendly by using low quality fuel and reducing the harmful effects of greenhouse gases.
An additional goal of the present invention is to provide a system and method, which minimizes water treatment costs.
It is still a further object of the present invention to provide a method for steam production and gas mixing for extraction of heavy bitumen.
It is an object of the present invention to provide a method for producing super-heated, dry, solid-free steam and gas mixture flow being between 800 and 4000 Kpa and in temperature of between 170° C. and 450° C.
It is still a further object of the present invention to provide a method that uses disposal water, possibly with oil, clay or silica sand from a SAGD facility.
It is still a further object of the present invention to provide a system for oil recovery using heat injection.
These and other objects and advantages of the present invention will become apparent from a reading of the attached specification and appended claims.